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Port 1647 (rsap)

IANA assigns port 1647 to rsap.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
rsap TCP rsap Holger Reif -
rsap UDP rsap Holger Reif -

Check what is listening on port 1647

Linux: is anything listening on TCP 1647?
sudo ss -tlnp 'sport = :1647'
Linux: UDP 1647
sudo ss -ulnp 'sport = :1647'
Linux / macOS: which process owns the port
sudo lsof -nP -i :1647
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':1647 '
Windows (Command Prompt)
netstat -ano | findstr :1647
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1647 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 1647
From Windows
Test-NetConnection HOST -Port 1647
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 1647

Block port 1647 in the firewall

ufw
sudo ufw deny 1647/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 1647 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 1647 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 1647' -Direction Inbound -Protocol TCP -LocalPort 1647 -Action Block
ufw
sudo ufw deny 1647/udp
iptables
sudo iptables -A INPUT -p udp --dport 1647 -j DROP
nftables
sudo nft add rule inet filter input udp dport 1647 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 1647' -Direction Inbound -Protocol UDP -LocalPort 1647 -Action Block

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All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.